The alignment of permanent mandibular incisors in children. A longitudinal prospective study.

The aim was to study the alignment of mandibular incisors before and after eruption of the canines, and if possible to find a method of predicting space deficiency. Fifty-three children with normal occlusion or untreated mild post-normal occlusion had plaster models taken at 7, 9, 10, and 13 years of age. An estimation of the space situation for the mandibular incisors was made using a scale with five levels. Measurements of intercanine distance, width of each incisor and space available between the canines were made. Greater crowding was seen before the eruption of permanent canines than after the start of eruption. Estimation of space showed significant correlations to measurements of inter-canine distance. Children with an excess of incisal space had a wider mandibular inter-canine distance compared with those with a deficiency of space. Among 7-, 9-, and 10-year-old children an inter-canine distance of less than 26 mm was associated with crowding. A distance of 28 mm or more was estimated as no risk for crowding.